Role of nitrogen transport for efficient energy conversion potential in low carbon and high nitrogen/phosphorus wastewater by microalgal-bacterial system

Microalgal-bacterial system (MBS) is potential biotechnology in wastewater treatment because it can remedy defects of conventional processes (e.g., insufficient carbon source and imbalanced elements ratio). However, the mechanisms of nitrogen (N) transport and removal in MBS are still unclear. In this study, it was discovered that MBS was conducive to adsorb NH₄⁺-N and NO₃^–-N through electrical neutralization, while extracellular polymeric substances (EPS) could provide binding sites (e.g., –OH and –CH₃) for enhancing N transport and removal. The microalgae-bacteria interaction could accelerate N transport and removal from aqueous solution to cell. More importantly, the microalgal starch biosynthetic metabolism exhibited demonstrating the energy production potential could be boosted via MBS. Overall, the NO₃^–-N and NH₄⁺-N removal efficiencies, and energy yield were 82.28%, 94.15%, and 86.81 kJ/L, respectively, which are better than other relevant studies. Altogether, it is meaningful for revealing the applicability of MBS for treating wastewater and producing energy.